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How can you tell if your cars drivetrain is set up correctly before you come to the track?
One of the best ways to make sure your car is set up before you turn a wheel at the track is to do a little homework to make sure the drivetrain is as good as it can be. One of the best tools to use to make sure your cars drivetrain is set up properly is a……..spreadsheet. Yes, a spreadsheet. The best place to start with making sure your car is up to speed is to actually check the speed before you hit the track.
Tools Required
- Digital Tachometer. Don’t have one? You can either buy one on eBay for $15 or use the clubs digital tachometer.
- Computer with Excel
- Set up Spreadsheet – attached to this article
1. Measure the RPM of your motor. Use the digital tachometer to measure the RPM of the motor at 11v. Enter that number into the spreadsheet
What are you looking for? You want a motor that is turning 18,500 to 22,500 RPM. If your motor is outside of that range you want to look for a different motor.
2. Enter the crown and pinon gear you plan on using to get your wheel calculated RPM to hit 7,000 to 7,800.
What are you looking for? Once you have a motor you want you can select the proper gearing to give you the proper RPM at the wheel. The spreadsheet will allow you to enter different pinion and crown gear sizes to see what the best combination is to achieve the desired wheel RPM.
3. Install the gearing you have selected and measure the RPM of the wheel.
What are you looking for? It depends a lot on your driving style, your experience level, how stable your car is, the overall weight of the car and the rear tire diameter. Having said all of that you usually want to end up with a wheel RPM of 7,000 to 7,800. Once again, this all depends on the stipulations listed above. Be aware that a car running 7,000 RPM with a 22mm diameter rear tire is much faster on the straights than a car running 7,000RPM with a 20mm diameter rear tire.
4. Check to see what the difference is between the calculate wheel RPM and the actual wheel RPM you measured.
What are you looking for? If the difference is greater than 10% you might have an issue with your drivetrain that is stealing energy from your wheels. Go back and check the gear mesh and the axle bushings to make sure everything is running as smooth as possible.
Good luck with this and don’t hesitate to see me at the track if you have any questions.